In internal combustion engines, pistons are housed within corresponding cylinders for reciprocating movement therein. Fuel and air enter a combustion chamber in a cylinder on a first side of a piston. The fuel in the combustion chamber is ignited to cause linear motion of the piston inside the respective cylinder. The linear motion of the piston is then converted to rotary motion by the crankshaft. Ideally, all of the gases in the combustion chamber(s) after ignition of the fuel would be exhausted via an engine exhaust pipe. However, a portion of the exhaust gases typically pass past the piston rings and the cylinder walls of the cylinders housing the pistons to enter the crankcase. These exhaust gases build up in the crankcase thereby pressurizing the crankcase. During routing of the exhaust gases within the crankcase, the gases often become contaminated with oil mist/oil droplets, the mixture of which is known as crankcase blow-by, or simply blow-by.
To relieve such exhaust gases from the crankcase, a breather assembly, joining the crankcase to an air intake point (e.g., an air cleaner or intake manifold), is typically attached to, or incorporated into, the internal combustion engine. A one-way valve is additionally placed in-line at an entrance hole between the breather assembly and the crankcase, such that gases escaped from the crankcase cannot return thereto. Frequently, along with the exhaust gases, some oil mist/oil droplets are invariably expelled into the breather assembly. In at least some conventional breather assemblies, at least some of the oil mist/oil droplets that pass into the breather assembly are trapped therein and tend to flow back into the crankcase due to pressure differentials and gravity via a drainback conduit.
Utility engines with breather assemblies are typically used with small power equipment, such as a lawnmower. In applications such as lawnmowers, the engine is often tilted, as would happen when cutting on a hill. Tilting an engine during operation can allow more blow-by gas that is laden with oil droplets to enter the breather assembly. Typically, for optimal removal of oil droplets from blow-by gas, an engine's breather assembly is distanced vertically upwards as far as possible from the oil reservoir. The substantial distance between the breather assembly and the oil reservoir allows gravity to remove more of the oil particles from the blow-by gas before the blow-by gas enters the breather assembly. Additionally, the distance allows the engine to be tilted off a vertical axis point while in use without significantly increasing the amount of oil droplets in the blow-by gas that enters the breather assembly, and therefore it prevents much of the blow-by gas that is heavily laden with oil droplets from entering the breather assembly and being pulled by engine vacuum or pushed by the crankcase pressure into the air intake point. The intake of substantial oil droplets in the air intake point of an engine results in excessive oil being exhausted to the engine cylinder where it is burned, thereby increasing engine oil consumption and producing excessive smoke.
Due to the particular configurations of horizontal and vertical crankshaft engines and the desire to maintain the breather entrance hole as far above the oil reservoir as possible, varied designs are often required to accommodate the breather assembly placement; this in turn limits the interchangeability among their engine components.
It would therefore be advantageous to provide an improved breather assembly that at least partially reduces the amount of oil droplets introduced into the breather assembly, particularly when an engine is tilted, as can occur during typical engine use. It would further be advantageous if such a breather assembly can provide at least some interchangeability among horizontal and vertical crankshaft engine components.